Editing post and page responding 503 Service Unavailable

Your scripts might be stuck in infinite loop, not producing a fatal error but causing the server to timeout the request after some time. Try installing xdebug for your OS/distribution (php-xdebug in recent Ubuntu versions) which will enforce a xdebug.max_nesting_level directive that should log an actual error and a call stack to help you identify the problem.

Hata!: SQLSTATE[HY000] [1045] Access denied for user 'divattrend_liink'@'localhost' (using password: YES)